1. Field of the Invention:
The present invention relates to an apparatus for supplying air or other fluid to a user on demand. More particularly, the present invention relates to such an apparatus for use in an underwater breathing system, such as a scuba system.
2. Description of Related Art:
Scuba diving is a sport enjoyed around the world. Diving as a sport has been around for several decades, but it has only been recently that the dive industry has attempted to make diving gear that is comfortable, attractive, compact and light weight.
Conventional scuba regulators consist essentially of two parts. A first stage fits on the tank which is attached to the user's back. The tank contains air or other gas pressurized to between 2,000 and 4,000 psi when full. The first stage lowers the air intermediate pressure of the air leaving the tank to a constant pressure of about 130 psi above the ambient pressure out of the "low pressure" port, regardless of the remaining tank pressure.
The air from the first stage flows to the second stage through a flexible tube. The second stage includes a valve structure which supplies the pressurized air to the user on demand. Typically, this is accomplished by a diaphragm which moves in response to the inhalation of the user causing a valve to let air escape for the user. Upon the user exhaling, the diaphragm returns to its original position and the exhaled gas is removed from the regulator through an appropriate exhaust valve.
However, conventional regulators have several shortcomings. They are quite bulky due to the large inhalation diaphragm which operates the second stage valve. This large size is not only unattractive but increases the manufacturing costs and results in the regulators being unnecessarily heavy.
The conventional regulator diaphragm is in the form of a circular disk. The diaphragm applies a force to the second stage valve proportional to the pressure differential on either side of the diaphragm (caused by inhaling) times the effective surface area of the diaphragm. In particular, the effective surface area equals .pi.D.sup.2 /4, where D is the diameter of the circular diaphragm. If the diaphragm has a diameter of 2.5 inches, the surface area will be 4.9 square inches.
Recently a new type of regulator has appeared which overcomes some of the problems of the conventional regulator. These regulators, known as "servo assisted" regulators use a smaller inhalation diaphragm but with a pneumatic amplifier system in the second stage to amplify the diver's breathing signal. In such systems are shown in U.S. Pat. No. 4,219,017 and in Applicant's U.S. Pat. No. 4,494,537. In such devices an inhalation diaphragm mounted on the casing is movable in response to user's demand but does not directly control the air supply valve. Instead, the inhalation diaphragm controls a sensitive pilot valve through a control lever which in turn controls the air flow. However, designs requiring pilot valves have certain shortcomings, amongst them are a relatively complex structure involving numerous parts, high manufacturing costs and a less rugged regulator.